Making unsaturated ethers of cellulose



Patented 1-35.25, 1941 233L927 I V UNITED. STATES PATENT OFFlCE Floyd 0. i'eterson and Arthur 1. Barry, Midland, Mich, assignors to The Dow Chemical Conn pany, Midland, Micln, a corporation of Michi- No Drawing. Application January 28, 1939,

Serial No. 258,445

10mm. (cl. ace-2'31) v This invention relates to s method for the converted byside reactions into undesired secpreparation of unsaturated ethers of cellulose ondary products. The unsaturated ethers of; cel- 'andespeeially such a method; carried out at lulose heretofore produced',when first prepared, low temperatur in the presence of anhydrous have been insoluble, .or but slightly soluble in 5 liquid ammonia. i the customary. solvents for alkyl ethers-of cel- 5 In a co-pending application, Serial No. 187,655, lulose. This is presumed to be due to the polyilled January 29, 1938, now U; 8. Patent No. merlzation of unsaturated cellulose ethers at the 2,157,083, issued May 2, 1939, of which the present elevated temperatures employed in the .etheriflappllcationis a continuation-in-part, there is cation reaction.

o disclosed a new method for the .preparation of It is accordingly among the objects of the incellulose ethers. The said new method comprises vention to provide a low temperature method for reacting substantially anhydrous cellulose with the prep of unsaturated e h rs of eelan alkali metal in amedium comprising anhylulose. It is a par i u r object'to Pr v uch. drous liquid ammonia, and in the presence of'a a method whereby the unsaturated cellulose 1 liquid hydrocarbon such as toluene which i ethers may be obtained in a'solvent-soluble, subinert to the celluloseand liquid ammonia, and s ially unpolymeri ed ormsubstantially inert to the action of alkali metal. According-t0 the inv n on. n i l y ym; reaction produces an 11 gellulogate drous cellulose is suspended in anhydrous liquid which is thereafter reacted in a liquid ammonia ammonia and converted to an alkali cellulosate 9 medium with an etherlfylng agent h h, i th according to either of the methods described in 20, aforesaid co-pending application, was defined as the aforesaid -p s. app ica ions. Serial an alkyl or aralkyl halide or sulphate or sub- Nos- 187,654-5- -Regard f the manner s i ion products of such compounds. which. the alkali cellulc'sate is prepared in the In anoth r 1' our co-pendlng applications, liquid ammonia medium, after the reaction has 7 Serial No. 187,654, flied January 29, 1938 now ne o completi n. there may be added to the) U. 8. Patent No. 2,145,273, issued January 31, suspension of alkali n iquld ammonia 1939, there is disclosed and claimed a method for ,m ated aliphatic or, aryl aliphatic l de the preparation of alkyl or aralkyl ethers of celslfl h Examples of the preferred etherifylulose comprising first reacting cellulose with an agents are 911191 bromide, yl ellyl realkali amide in liquid ammonia, and then etherimide, cinn mol omide, crotonyl br mid etc- 3 tying the so-formed alkali cellulosate. The correspon ing chlorides 01' sulph s y be .The present invention is concerned with a used. Tothe alkalicellulosate is added from 1 method for the preparation of unsaturated ethers n preferably from 3 to 5, q alent of cellulose. such as the allyl, z-methyl allyl, weights of n a ura e h r ins agent per crotyl and einnamyl ethers, all of whi h hav an atom of alkali metal in the cellulosate. There 35 olefinic double bond in the aliphatic residue. may v be D -d in the reaction Vessel a liquid Allyl cellulose, which is'typical of the group, has aromatic h c to serve as a ispersion been prepared heretofore by the customary methagent Solvent the cellulose e her. After ods applied to the formation of cellulose ethers. the y s agent ha en ded to the cel my Cellulose ethers are usually prepared from alkali ulo 1n the desired proportion t mixture is 40 cellulose rather than from alkali metal hyallowed to stand, pr a ly with occasional droxylates of cellulose. Th alkali llul agitation, untilthe etherification reaction is comusuallyemployed is prepared by treating eelple t This Or in ily q fl from 3 to 24 w lulose with aqueous caustic alkali. In such methhe s n m t f q n ly i fi h in from 8 5 ods a, large excess of alkali is required, the alkali to 12 hours, depending up the etherifrihs 4 q cellulose product contains water, arui is often agents employed. the temperature of the e h n not uniform in composition. In the preparation and the number of atoms of alkali metal subof cellulose ethers from such aqueous alkali lstituted in the cellulose molecule. The temperaso lulose prepared as aforesaid, the latter is reacted ture f h rifl i n m y range from -80 6.

with an etherifying agent by heating together to +25 C. and the reaction is carried out under under pressure for several hours' For the rethe corresponding vapor pressure of liquid amaction, a very large excess of etherifying agent monia. For ease of operation, temperatures required, much of which at the temperature near 33 0., the boiling point of liquid ammonia,

f the reaction and; in the presence of water, is are preferred. We prefer to carry out the etherification reaction while the liquid ammonia is at atmospheric pressure and while it is being allowed to volatilize slowly away from the reaction mixture. Due to the low or moderate temperature employed in the etheriflcation reaction and to the absence of 'water, side reactions and decomposition of etherifying agent are reduced to a minimum and the excess of etherifying agent can be substantially recovered as such from the reaction product.

The following examples illustrate the practice of the invention:

Example 1 162 parts (1 mole) of cellulose and 69 parts (3 moles) of sodium are reacted in 3200 parts of liquid ammonia in the presence of 500 parts of toluene at 33 C. When the reaction is complete, as evidenced by the disappearance of the blue color of sodium in liquid ammonia, the ammonia is allowed to volatilize until 900 parts thereof remain in the reaction vessel. 410 parts (5 moles) of allyl chloride dissolved in 1000 parts of toluene are slowly poured into the sodium cellulosate suspension while the mixture is agitated and while the temperature is held at or near --33 C. This temperature is maintained for about 8 hours and the mixture is then allowed to warm up gradually to about 25 C., the ammonia distilling away from the reaction product in the meantime. The product is washed with petroleum ether to remove excess reagent, is dissolved in a solvent mixture of 80 parts toluene and 20 parts ethanol by volume, and centrifuged to remove unetherified fibrous material. The solution so-obtained contains 1'75 parts by weight of allyl cellulose which can be cast into films, spun into fibers, and otherwise handled in a manner similar to that employed in connection with the usual solvent-soluble ethers of cellulose. When the solution or any product deposited therefrom is heated to a temperature in the range from 60 to 100 C., the allyl cellulose becomes insoluble, indicating that polymerization is occurring.

Example 2 94 parts (4 moles) of sodium was added to 4300 parts of liquid ammonia in the presence of a' vture was stirred and the ammonia allowed to evaporate slowly until only sufficient ammonia (approximately 180 parts) remained to keep the alkali cellulosate moist with ammonia. To the mixture was added 680 parts (6 moles) of allyl bromide in 2300 parts of toluene. The resulting reaction mixture was thoroughly agitated while the temperature was held at or below 33 C. for about 10 hours, and then allowed to rise to 25 C. while the remaining ammonia boiled off. There was obtained 272 parts of allyl cellulose which was soluble in 80/20 toluene-ethanol solvent and which, when heated, deposited the insoluble, polymerized variety of allyl cellulose.

Example 3 lose was soluble in the usual organic solvents for cellulose ethers.

The unsaturated ethers of cellulose are particularly desirable because of their potential insolubility in many of the customary solvents.

This insolubility is preferred after fabrication, rather than before. They have heretofore been difficult to handle because they have been converted to the insoluble form in most instances during the etherification reaction. The present invention provides a convenient method for producing the unsaturated ethers of cellulose in a solvent-soluble form so that they may be handled readily and fabricated into the desired articles prior to subjecting them to the action of heat, ultra-violet light, or other of the known polymerizing or insolubilizing agents for unsaturated cellulose ethers.

Other modes of applying the principle of our invention may be employed instead of those ex- After about 10 plained, change being made as regards the meth- 0d and material herein disclosed, provided the step or reactants stated by the following claim, or the equivalent of such stated step or reactants, be employed.

We therefore particularly point out and distinctly claim as our invention:

The method which comprises reacting an alkali metal cellulosate, in a medium comprising liquid ammonia and toluene, at a temperature of about 33 C., with an excess 'over the theoretical amount of an allyl halide, for about 8 to 10 hours, removing remaining ammonia while allowing the mixture to warm up to about 25 0., and, by removal of toluene, recovering the so-formed allyl ether of cellulose in a form which is soluble in 80/20 toluene-ethanol, and which, when heated to a temperature of from 60 to 100 C., is convertible to the insoluble, polymerized variety of allyl cellulose.

FLOYD C. PETERSON. ARTHUR J. BARRY. 

